how to fix P0420 code on Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Allow the exhaust system to cool down before working.

2. Inspect and Repair Exhaust Leaks

• Inspect the exhaust manifold, pipes, and joints for leaks.
• If leaks are found, use exhaust repair tape or replace gaskets and seals as needed.
• Reconnect any disconnected parts and ensure tight seals.

3. Replace Faulty Oxygen Sensors

• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Using a socket or wrench, carefully unscrew the faulty sensors and remove them.
• Install new oxygen sensors, tightening them to manufacturer specifications (usually around 30 lb-ft).
• Reconnect the electrical connectors.

4. Replace Catalytic Converter (if necessary)

• Disconnect the exhaust pipes from the catalytic converter by removing the bolts or clamps.
• Remove any mounting brackets holding the catalytic converter in place.
• Install the new catalytic converter, ensuring proper alignment.
• Reattach exhaust pipes and secure all connections with the appropriate torque (typically 20-30 lb-ft).

5. Reset the ECU

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code from the ECU.